网络应用程序对于数据收集/摄取很有用。如果收集和存储数据的机制易于使用,则可以积累大量有用的数据进行数据处理。将数据从一个位置移动到另一个位置的一种简单方法是 Web 应用程序上的拖放功能。
在这篇文章中,我展示了三个示例,说明如何使用 JavaScript 拖放编程来移动和存储 HTML 元素数据和文件。
<!DOCTYPE html> <html> <head></head> <body> <h1>Example 0: Drag and Drop HTML text/elements</h1> <div id="HTML_text" draggable="true" class="dragElement">HTML text</div> <br><br> <div id="dropArea" class="dropArea"> Drop for Example 0 & 1</div> <style> .dropArea { height: 200px; width: 200px; border-radius: 15px; border: 0.25px solid black; background-color: #7084c4; } .HTML_text { cursor: move; } </style> <script> var example; var other_data_related_to_dragEvent = {}; var html_element_drag_list_metaData = []; // ---------------------------------------------------- // Drag functionality: Example 0 // ---------------------------------------------------- document.getElementById("HTML_text").addEventListener("dragstart", processEvent_drag_example0, false); // document.getElementById("HTML_text").addEventListener("dragend", processEvent_drag_example0, false); // to stop function processEvent_drag_example0(event) { example = 0; event.dataTransfer.setData('text/plain', event.target.id); } // ---------------------------------------------------- // ---------------------------------------------------- // Drop functionality: Example 0 and 1 // ---------------------------------------------------- document.getElementById("dropArea").addEventListener("drop", processEvent_drop, false); document.getElementById("dropArea").addEventListener("dragover", processEvent_dragover, false); function processEvent_drop(event) { // Stop defaults and allow drop events event.preventDefault(); // Detects files dragged from pc html_element_drag_list_metaData.push(event.dataTransfer.files); console.log('html_element_drag_list_metaData: ', html_element_drag_list_metaData); // Detects html elements dragged from the html page const data = event.dataTransfer.getData('text/plain'); console.log('data: ', data); if (data.length != 0) { // find the draggable element based on the data const dragElement = document.getElementById(data); console.log('dragElement: ', dragElement); // Append the draggable element event.target.appendChild(dragElement); } } function processEvent_dragover(event) { // Stop defaults and allow drop events event.preventDefault(); } // ------------------------------------------------- </script> </body> </html>
在示例 0 中,HTML 文本元素实际上已移至放置区域。 HTML 文本的 div 的 id 出现在变量数据中,因此可以跟踪 dropArea 内的元素 id。此示例对于组织/存储在 Web 应用程序上编写的现有 html 非常有用,但在大多数数据摄取情况下,人们希望组织/存储来自不同位置的数据。
此示例是拖动 HTML 元素和拖动文件之间的交叉示例。可以使用“浏览”按钮选择一个文件;将文件拖到浏览按钮或单击浏览按钮选择文件。选择文件后会出现一个表情符号,表情符号的出现以 HTML 元素的形式表示该文件。然后可以将代表文件的 HTML 元素 emoji 拖到 dropArea 进行数据摄取/存储。
<!DOCTYPE html> <html> <head></head> <body> <h1>Example 1: Click button create drag and drop elements</h1> <input type="file" id="upload_file" accept="audio/*" style="display:block" multiple> <div id="file_name" style="display:none"></div> <div id="base64_string" style="display:none"></div> <div id="base64_string_icon" draggable="true" class="dragElement" style="display:none">?</div> <br><br> <div id="dropArea" class="dropArea"> Drop for Example 0 & 1</div> <style> .dropArea { height: 200px; width: 200px; border-radius: 15px; border: 0.25px solid black; background-color: #7084c4; } .HTML_text { cursor: move; } </style> <script> var example; var other_data_related_to_dragEvent = {}; var html_element_drag_list_metaData = []; // ---------------------------------------------------- // Drag functionality: Example 1 // ---------------------------------------------------- // The eventlistener needs to be always running, to detect which file the user selected with browse document.getElementById("upload_file").addEventListener("change", previewInput_drop, false); async function previewInput_drop(event) { // Take the first file const file = event.target.files[0]; // first file in the list of selected files, better for selecting multiple files at one time // console.log("file :", file); document.getElementById("file_name").innerHTML = file.name; // --------------------- const reader = new FileReader(); reader.onload = async function(e){ document.getElementById("base64_string").innerHTML = e.target.result; document.getElementById("base64_string_icon").style.display = "block"; } reader.readAsDataURL(file); } document.getElementById("base64_string_icon").addEventListener("dragstart", processEvent_drag_example1, false); function processEvent_drag_example1(event) { example = 1; event.dataTransfer.setData('text/plain', event.target.id); } // ---------------------------------------------------- // ---------------------------------------------------- // Drop functionality: Example 0 and 1 // ---------------------------------------------------- document.getElementById("dropArea").addEventListener("drop", processEvent_drop, false); document.getElementById("dropArea").addEventListener("dragover", processEvent_dragover, false); function processEvent_drop(event) { // Stop defaults and allow drop events event.preventDefault(); // Detects files dragged from pc html_element_drag_list_metaData.push(event.dataTransfer.files); console.log('html_element_drag_list_metaData: ', html_element_drag_list_metaData); // Detects html elements dragged from the html page const data = event.dataTransfer.getData('text/plain'); console.log('data: ', data); if (data.length != 0) { // find the draggable element based on the data const dragElement = document.getElementById(data); console.log('dragElement: ', dragElement); // Append the draggable element event.target.appendChild(dragElement); } } function processEvent_dragover(event) { // Stop defaults and allow drop events event.preventDefault(); } // ------------------------------------------------- </script> </body> </html>
在此示例中,可以一次高效地将多个文件拖动到 dropArea。
<!DOCTYPE html> <html> <head></head> <body> <h1>Example 2: Drag and drop files</h1> <input type="file" id="upload_file_dragdrop" style="display:block" class="dropArea1" multiple> <br><br> <button id="use_moved_data" onclick="use_moved_data()">use_moved_data</button> <!-- ---------------------------------------- --> <!-- CSS --> <style> .dropArea1 { height: 200px; width: 200px; border-radius: 15px; border: 0.25px solid black; background-color: #56b06e; } </style> <!-- ---------------------------------------- --> <script> var other_data_related_to_dragEvent = {}; var html_element_drag_list_metaData = []; // ---------------------------------------------------- // Drag and Drop functionality: Example 2 // ---------------------------------------------------- document.getElementById("upload_file_dragdrop").addEventListener("change", previewInput, false); async function previewInput(event) { // For multiple files const allFiles = event.target.files; // console.log("allFiles :", allFiles); var i = 0; while (i < allFiles.length) { const file = allFiles[i]; // console.log("file :", file); await obtain_fileInfo(file) .then(base64str => { other_data_related_to_dragEvent[file.name] = base64str; }) .catch(error => console.error(error)); i = i + 1; } // --------------------- } async function obtain_fileInfo(file) { var base64_string = await new Promise((resolve) => { const reader = new FileReader(); reader.onload = async function(e){ resolve(e.target.result); // inside resolve is the value that the function returns }; reader.readAsDataURL(file); }); return base64_string; } // ---------------------------------------------------- async function use_moved_data() { console.log('html_element_drag_list_metaData: ', html_element_drag_list_metaData); console.log('other_data_related_to_dragEvent: ', other_data_related_to_dragEvent); } </script> </body> </html>
我们可以看到拖入dropArea的三个文件的base64字符串数据!然后可以将 Base64 字符串数据保存为 Blob 对象并通过 Internet 传输。
我希望这些拖放 HTML 元素和文件的方法对某人有所帮助。
祝你练习愉快! ?
? GitHub | ?练习 Datscy @ Dev.to | ?练习 Datscy @ Medium
以上是拖放 HTML 元素和文件的详细内容。更多信息请关注PHP中文网其他相关文章!